Heat sealed sheet or film pouches are used for packaging certain products which are stored under sterile conditions. Typical of products stored under these conditions are certain foods and fluids used in medical care. In the packaging of food, the general class of packages is known as retort pouches. In the medical care business, representative products are fluids which are introduced into the patient by intravenous injection, the packages being commonly called I.V. bags, which nomenclature is adopted hereinafter.
Common to the requirements of I.V. bags is the requirement that the filled and sealed package be subjected to sterilizing conditions of relatively high temperature after the bag is filled with product and sealed. Typical sterilizing conditions range in severity up to about 250.degree. F. with residence times at that temperature of as much as 30 minutes or more. Such conditions impose severe stresses on the packages. Many otherwise acceptable polymeric materials are incapable of adequately protecting and holding the products under these processing conditions. Typically, problems are encountered with excessive weakening or failure of the heat seals about the periphery of the pouch. If a multiple layer sheet material is used in forming the bag, separations may develop between the layers during processing. Certain single layer polymeric structures, such as polyvinyl chloride, can survive the processing, but have other deficiencies.
Another requirement of an I.V. bag is that it retain its clarity after the autoclave processing. Manufacturers, packagers, and users of I.V. solutions require the ability to visually inspect the packaged product at all times. This allows any visually detectable changes in the product to be noted, as a further measure of the quality control and safety concerns of this highly safety-sensitive industry.
In dispensing of I.V. solution, it is desirable to be able to objectively estimate the rate of dispensing by observing, from time to time, the amount of solution gone from the bag. To this end, the bag is usually marked with volume, or scale marking along one side. Thus the bag must be dimensionally stable through the processing so that accurate volume readings may be taken.
After the packaging and sterilizing processes are complete, the packages must be capable of withstanding normal abuse of shipping, handling and use. Thus the requirements imposed on the package are relatively severe in that it must withstand severe processing conditions and, subsequently, be strong enough to accept physical handling abuse.
I.V. bags are commonly made of polyvinyl chloride-based (PVC) films. PVC bags, however, require the use of plasticizers to achieve needed flexibility in the film. There is a concern that the plasticizers may migrate into the product and cause undesirable effects on the user of the product. PVC films also allow passage of an undesirably high amount of moisture out through the film. This potential moisture loss could cause gradual compositional and volume change of the solution and could be a significant factor in determining product shelf life. To this end, conventional PVC bags are overwrapped with a moisture barrier material such as high density polyethylene.
Thus, it is desirable to provide an improved packaging structure for use with sterile products, wherein the package is sterilized after filling and sealing. The improved structure should be capable of withstanding sterilizing process conditions, including protecting and holding the product during the processing, and should emerge with strong heat seals about its periphery and with good integrity of the film structure. Particularly important is good adhesion between the layers, if a multiple layer film is used. For use with human contacting products, the package must, of course, be made of materials which have no, or very low, toxicity to humans. To the extent that a barrier to transmission of moisture can be provided at reasonable cost, this too, is desirable, and would allow elimination of the costly overwrapping. Finally, the bag must have good heat seals in order to contain the product and to minimize package failures due to rough handling.